Optical connectors may serve for optically connecting an optical fiber unit to another fiber unit or an optical fiber unit to other optical elements. The invention has an important application in optical fiber communications apparatus.
Optical connectors which make a mating connection are known for communications and for short-distance data links. Such connectors are suitable for optical cable transmission systems (simply called "FC connectors") and for optical subscriber systems (simply called "SC connector").
Conventional optical connectors, such as for example SC connectors, comprise a plug and an associated socket or receptacle (which is also sometimes referred to as an `adapter`).
The basic arrangement of these components is as follows: The plug comprises a ferrule with an optical fiber unit at its center. The fiber is concentrically surrounded by a sleeve and by a cylindrical jacket, in that order, made from ceramics, metal or polymer. The ferrule is held in a frame, and a positioning key is disposed on the periphery of the frame. A compression spring pushes the ferrule towards its forward end, and the frame itself is fixed to an inner wall surface of a plug housing.
Typically, a conventional receptacle comprises a resin housing which is injection-molded as a single unit. The housing has a cylindrical alignment sleeve extending within the housing in an axial direction. When the plug described above is fitted into the receptacle, the ferrule of the plug becomes aligned with the alignment sleeve. In this manner the end face of the optical fiber unit can be optically connected to and aligned with another optical fiber unit or to other optical elements on the same axis.
Generally, in an optical connector for data links the optical fiber unit is often connected directly to a light emitting device or a light receiving device. In the case of such an opto-electronic transducer module (or "active component"), the housing usually contains optical elements, such as light emitting and/or light receiving devices, and electric circuits, which together perform the conversion between optical and electric signals. The module is incorporated into the receptacle and the receptacle is connected to the plug so that the optical fiber unit is connected to the optical devices to enable the transmission and/or reception of dam.
Conventional optical connectors of the kind just described suffer from connection losses arising from structural defects such as an axial displacement and angle displacement when connecting the optical fiber trait to the optical elements.
Also, to achieve satisfactory axial alignment the inner diameter of the alignment sleeve must closely match the outer diameter of the ferrule, which requires the use of highly accurate manufacturing techniques. Any mounting portions and alignment sections, etc., need also to be accurately formed in the receptacle. To achieve high alignment accuracy, conventional receptacles need to have their alignment sleeve machined in an accurately axial direction. Because of the required degree of accuracy, the interior of the sleeve needs to be formed by a precision machining operation, which creates difficulties in manufacturing. Furthermore, conventional methods such as that described so far, also require that the optical connector be made up of a considerable number of different and/or complex components parts. It is difficult therefore to make a standard product which nevertheless ensures stable connections.
Similar problems arise also with other types of optical connector.